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Ronny M. Gouveia
ISEP—School of Engineering, Polytechnic of Porto, 4200-072 Porto, Portugal

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Journal article
Published: 13 May 2020 in Materials
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Additive manufacturing allows for a great degree of design freedom and is rapidly becoming a mainstream manufacturing process. However, as in all manufacturing processes, it has its limitations and specificities. Equipping engineers with this knowledge allows for a higher degree of optimization, extracting the most out of this technology. Therefore, a specific part design was devised and created via L-PBF (Laser Powder Bed Fusion) using AlSi10Mg powder. Certain parameters were varied to identify the influence on material density, hardness, roughness, residual stress and microstructures. It was found that on heat treated parts laser pattern strategy is one of the most influential aspects, showing that chessboard and stripes 67° improved outcome; average Ra roughness varied between 8–12 µm, residual stress was higher on vertical surfaces than horizontal surfaces, with the combination of support structures and stripes 67° strategies generating the lowest residual stress (205 MPa on a lateral/vertical face), hardness was non-orientation dependent and larger on samples with chessboard fabrication strategies, while microstructures were composed of α–Al dendrites surrounded by Si particles. The distribution and grain size of the microstructure is dependent on location regarding melt pool and HAZ area. Furthermore, Al–Mg oxides were encountered on the surface, along with pores generating from lack of fusion.

ACS Style

Ronny M. Gouveia; Francisco J. G. Silva; Eleonora Atzeni; Dušan Sormaz; Jorge Lino Alves; António Bastos Pereira. Effect of Scan Strategies and Use of Support Structures on Surface Quality and Hardness of L-PBF AlSi10Mg Parts. Materials 2020, 13, 2248 .

AMA Style

Ronny M. Gouveia, Francisco J. G. Silva, Eleonora Atzeni, Dušan Sormaz, Jorge Lino Alves, António Bastos Pereira. Effect of Scan Strategies and Use of Support Structures on Surface Quality and Hardness of L-PBF AlSi10Mg Parts. Materials. 2020; 13 (10):2248.

Chicago/Turabian Style

Ronny M. Gouveia; Francisco J. G. Silva; Eleonora Atzeni; Dušan Sormaz; Jorge Lino Alves; António Bastos Pereira. 2020. "Effect of Scan Strategies and Use of Support Structures on Surface Quality and Hardness of L-PBF AlSi10Mg Parts." Materials 13, no. 10: 2248.

Journal article
Published: 30 November 2019 in Metals
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Residual stresses (RS) of great magnitude are usually present in parts produced by Laser Powder Bed Fusion (PBF-LB), mainly owing to the extreme temperature gradients and high cooling rates involved in the process. Those “hidden” stresses can be detrimental to a part’s mechanical properties and fatigue life; therefore, it is crucial to know their magnitude and orientation. The hole-drilling strain-gage method was used to determine the RS magnitude and direction-depth profiles. Cuboid specimens in the as-built state, and after standard solution annealing and ageing heat treatment conditions, were prepared to study the RS evolution throughout the heat treatment stages. Measurements were performed on the top and lateral surfaces. In the as-built specimens, tensile stresses of ~400 MPa on the top and above 600 MPa on the lateral surface were obtained. On the lateral surface, RS anisotropy was noticed, with the horizontally aligned stresses being three times lower than the vertically aligned. RS decreased markedly after the first heat treatment. On heat-treated specimens, magnitude oscillations were observed. By microstructure analysis, the presence of carbides was verified, which is a probable root for the oscillations. Furthermore, compressive stresses immediate to the surface were obtained in heat-treated specimens, which is not in agreement with the typical characteristics of parts fabricated by PBF-LB, i.e., tensile stresses at the surface and compressive stresses in the part’s core.

ACS Style

Rafael Barros; Francisco J. G. Silva; Ronny M. Gouveia; Abdollah Saboori; Giulio Marchese; Sara Biamino; Alessandro Salmi; Eleonora Atzeni. Laser Powder Bed Fusion of Inconel 718: Residual Stress Analysis Before and After Heat Treatment. Metals 2019, 9, 1290 .

AMA Style

Rafael Barros, Francisco J. G. Silva, Ronny M. Gouveia, Abdollah Saboori, Giulio Marchese, Sara Biamino, Alessandro Salmi, Eleonora Atzeni. Laser Powder Bed Fusion of Inconel 718: Residual Stress Analysis Before and After Heat Treatment. Metals. 2019; 9 (12):1290.

Chicago/Turabian Style

Rafael Barros; Francisco J. G. Silva; Ronny M. Gouveia; Abdollah Saboori; Giulio Marchese; Sara Biamino; Alessandro Salmi; Eleonora Atzeni. 2019. "Laser Powder Bed Fusion of Inconel 718: Residual Stress Analysis Before and After Heat Treatment." Metals 9, no. 12: 1290.

Journal article
Published: 17 June 2019 in Coatings
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In the last decade, it has been common to observe a competition between coatings achieved via physical vapor deposition (PVD) and chemical vapor deposition (CVD) techniques on cutting tools used in machining processes. The tool’s substrate material can immediately condition the coating process selection. However, there are also materials capabe of adapting to any of the coating processes. Hence, the capabilities demonstrated by a given coating when created with one technique or another are usually different due to the intrinsic characteristics of each coating process, such as temperature and stress levels. In this work, to study the machining behavior of a super duplex stainless steel, PVD- and CVD-coated tungsten carbide inserts with different coatings were used in order to identify the wear mechanisms that affect each of the coatings and the workpiece’s surface quality, evaluated through different roughness parameters. The vibration level produced throughout the various tests was also registered in an attempt to associate the type of coating or insert failure with the level of vibrations generated in the CNC (Computer Numeric Control) machining spindle. This allowed us to conclude that the tools coated with TiAlN via PVD showed better wear behavior, as well as creating workpiece surfaces with less roughness. Thus, it was clear that this coating presents strong advantages in the machining of the super duplex stainless steel chosen for this work, being an innovative work due to the combination of materials used and the approach in terms of vibration analysis applied to milling.

ACS Style

Francisco José Gomes Silva; Rui Pedro Martinho; Carlos Martins; Hernâni Lopes; Ronny Miguel Gouveia. Machining GX2CrNiMoN26-7-4 DSS Alloy: Wear Analysis of TiAlN and TiCN/Al2O3/TiN Coated Carbide Tools Behavior in Rough End Milling Operations. Coatings 2019, 9, 392 .

AMA Style

Francisco José Gomes Silva, Rui Pedro Martinho, Carlos Martins, Hernâni Lopes, Ronny Miguel Gouveia. Machining GX2CrNiMoN26-7-4 DSS Alloy: Wear Analysis of TiAlN and TiCN/Al2O3/TiN Coated Carbide Tools Behavior in Rough End Milling Operations. Coatings. 2019; 9 (6):392.

Chicago/Turabian Style

Francisco José Gomes Silva; Rui Pedro Martinho; Carlos Martins; Hernâni Lopes; Ronny Miguel Gouveia. 2019. "Machining GX2CrNiMoN26-7-4 DSS Alloy: Wear Analysis of TiAlN and TiCN/Al2O3/TiN Coated Carbide Tools Behavior in Rough End Milling Operations." Coatings 9, no. 6: 392.

Journal article
Published: 19 January 2018 in Metals
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The weldability of ductile iron, as widely known, is relatively poor, essentially due to its typical carbon equivalent value. The present study was developed surrounding the heat treatability of welded joints made with a high strength ductile cast iron detaining an ultimate tensile strength of 700 MPa, and aims to determine which heat treatment procedures promote the best results, in terms of microstructure and mechanical properties. These types of alloys are suitable for the automotive industry, as they allow engineers to reduce the thickness of parts while maintaining mechanical strength, decreasing the global weight of vehicles and providing a path for more sustainable development. The results allow us to conclude that heat treatment methodology has a large impact on the mechanical properties of welded joints created from the study material. However, the thermal cycles suffered during welding promote the formation of ledeburite areas near the weld joint. This situation could possibly be dealt through the implementation of post-welding heat treatments (PWHT) with specific parameters. In contrast to a ductile cast iron tested in a previous work, the bull-eye ductile cast iron with 700 MPa ultimate tensile strength presented better results during the post-welding heat treatment than during preheating.

ACS Style

Ronny M. Gouveia; Francisco J. G. Silva; Olga C. Paiva; Maria De Fatima Andrade; Lucas Augusto Pereira; Paulo Cezar Moselli; Konrad J. M. Papis. Comparing the Structure and Mechanical Properties of Welds on Ductile Cast Iron (700 MPa) under Different Heat Treatment Conditions. Metals 2018, 8, 72 .

AMA Style

Ronny M. Gouveia, Francisco J. G. Silva, Olga C. Paiva, Maria De Fatima Andrade, Lucas Augusto Pereira, Paulo Cezar Moselli, Konrad J. M. Papis. Comparing the Structure and Mechanical Properties of Welds on Ductile Cast Iron (700 MPa) under Different Heat Treatment Conditions. Metals. 2018; 8 (1):72.

Chicago/Turabian Style

Ronny M. Gouveia; Francisco J. G. Silva; Olga C. Paiva; Maria De Fatima Andrade; Lucas Augusto Pereira; Paulo Cezar Moselli; Konrad J. M. Papis. 2018. "Comparing the Structure and Mechanical Properties of Welds on Ductile Cast Iron (700 MPa) under Different Heat Treatment Conditions." Metals 8, no. 1: 72.

Journal article
Published: 19 September 2017 in Metals
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Nowadays, ultimate tensile strengths above 400 MPa become usual for ductile irons, thus allowing the implementation of new design paradigms. Large concentrations of carbon and other influencing elements can negatively interfere with the welding process of ductile cast irons. Efforts made by researchers have led to the discovery of solutions which enable good enough operational results to consider welding as a viable repairing or joining method. Although these alloys have been available for quite some time, researchers have mainly focused on issues relating to microstructural phenomena tied to casting and similar processes, leaving much to explore in terms of their weldability. Thus, this work intends to investigate the effect of different heat-treatments on the weldability of a high strength ductile cast iron by assessing the mechanical properties of welded joints as well as structural modifications induced by thermal cycles imposed before and after welding. Successful weld joints were achieved showing a clear heat affected zone (HAZ) close to the joint area. This area is coincident with the fracture area of the welded samples when loaded on a tensile test bench, having obtained promising results regarding mechanical strength and strain. The hardness of the welded zone was also carefully investigated, showing clear changes throughout the joint.

ACS Style

Ronny M. Gouveia; Francisco J. G. Silva; Olga C. Paiva; Maria F. Andrade; Luiz Silva; Paulo C. Moselli; Konrad J. M. Papis. Study of the Heat-Treatments Effect on High Strength Ductile Cast Iron Welded Joints. Metals 2017, 7, 382 .

AMA Style

Ronny M. Gouveia, Francisco J. G. Silva, Olga C. Paiva, Maria F. Andrade, Luiz Silva, Paulo C. Moselli, Konrad J. M. Papis. Study of the Heat-Treatments Effect on High Strength Ductile Cast Iron Welded Joints. Metals. 2017; 7 (9):382.

Chicago/Turabian Style

Ronny M. Gouveia; Francisco J. G. Silva; Olga C. Paiva; Maria F. Andrade; Luiz Silva; Paulo C. Moselli; Konrad J. M. Papis. 2017. "Study of the Heat-Treatments Effect on High Strength Ductile Cast Iron Welded Joints." Metals 7, no. 9: 382.

Journal article
Published: 05 July 2017 in Metals
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Decreasing the weight of heavy-duty vehicles is an ongoing concern. However, the need to deal with high temperatures in components such as manifolds imposes, by itself, some restrictions regarding material selection, being further limited when other required properties (e.g., functional, manufacturing or cost requirements) are taken into account. Cast austenitic stainless steels may represent a good choice in this context but the existence of concentrated chromium carbides can generate undesirable results. A good combination of heat treatments can be applied to cast heat-resistant austenitic stainless steels, in an effort to achieve the dispersion of fine carbides, consequently improving their microstructure, mechanical properties and creep resistance. In this work, an austenitic stainless steel usually used in high temperature applications was characterized and subjected to solution annealing and aging heat treatments. The material analyzed was the austenitic cast stainless steel HK30 and the goals of the work were to evaluate the effects of solution annealing heat treatments on the dissolution of grain boundary chromium carbides and the effects of aging treatments on creep resistance. The results show that the elimination of grain boundary chromium carbides is possible by applying a solution annealing heat treatment. Additionally, the precipitation of fine dispersed carbides is obtained after the aging treatment with an increase of hardness and, consequently, an expected improvement of creep resistance. Thus, the novelty presented by this work consists of selecting the best heat treatment combination in order to promote dispersion of carbides, thus avoiding further crack nucleation phenomena when parts are cyclically subjected to load and unload; this work also found the most adequate mechanical properties and achieved corrosion resistance regarding the application in heavy-duty vehicle components subjected to mechanical and thermal fatigue. By discovering methods of improving the properties of cast materials, large savings can be made both in terms of production costs as well as in the overall weight of the components.

ACS Style

Francisco J. G. Silva; Jorge Santos; Ronny Gouveia. Dissolution of Grain Boundary Carbides by the Effect of Solution Annealing Heat Treatment and Aging Treatment on Heat-Resistant Cast Steel HK30. Metals 2017, 7, 251 .

AMA Style

Francisco J. G. Silva, Jorge Santos, Ronny Gouveia. Dissolution of Grain Boundary Carbides by the Effect of Solution Annealing Heat Treatment and Aging Treatment on Heat-Resistant Cast Steel HK30. Metals. 2017; 7 (7):251.

Chicago/Turabian Style

Francisco J. G. Silva; Jorge Santos; Ronny Gouveia. 2017. "Dissolution of Grain Boundary Carbides by the Effect of Solution Annealing Heat Treatment and Aging Treatment on Heat-Resistant Cast Steel HK30." Metals 7, no. 7: 251.